Forward-Swept Pressure Screen Rotor to Reduce Stringing Drag

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Solution Overview

Problem

Conventional pressure screen rotors for paper pulp processing experience stringing issues due to contaminants and fibers accumulating on the forward edges of struts and foils, leading to increased rotor drag and reduced effectiveness in dislodging contaminants, which in turn increases motor power requirements.

Innovation Solution

The implementation of forward-swept struts on the rotor, which create flow currents that redirect contaminants and fibers inboard towards the hub, reducing accumulation on the strut and foil edges, and incorporating a release region with increased thickness to facilitate smooth passage over the strut-hub connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional radially extending struts are used on the rotor, then the rotor structure is simple and easy to manufacture, but contaminants and fibers accumulate on the forward edges of the struts and foils, causing stringing and increased rotor drag

Engineering Contradiction:

Improverotor structure simplicityVSAvoidstringing and rotor drag

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent applies asymmetry by configuring the struts with a forward-swept geometry where the leading edge is angled relative to the radial direction. This asymmetric shape prevents contaminants and fibers from accumulating on the forward edges by creating flow currents that redirect them inboard toward the hub, thereby reducing stringing and rotor drag while maintaining manufacturing feasibility

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the geometric parameters of the struts by sweeping the leading edge forward at a specific angle relative to the radial direction. This parameter modification alters the flow characteristics around the struts, preventing contamination buildup and reducing the harmful effects of stringing without significantly complicating the manufacturing process

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the rotor rotates at high speed to maintain productivity, then the screening capacity increases, but the motor power required increases due to increased rotor drag from contaminant accumulation

Engineering Contradiction:

Improvescreening capacityVSAvoidmotor power consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The asymmetric forward-swept strut configuration reduces rotor drag by preventing contaminant accumulation, thereby lowering motor power consumption and allowing the rotor to maintain high speeds for sustained productivity without excessive energy input

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent converts the potentially harmful flow patterns around the struts into beneficial flow currents that actively redirect contaminants and fibers inboard. This transforms what would normally be drag-inducing flow separation into a useful mechanism for preventing stringing and reducing power consumption

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-generated harmful factors

If thicker struts are used to reduce stringing, then contaminant accumulation is reduced, but the rotor drag increases due to larger strut cross-sectional area

Engineering Contradiction:

Improvecontaminant accumulationVSAvoidrotor drag

Core Design Contradiction:

Object-generated harmful factorsVSForce

Solution Approach 1:

The asymmetric forward-swept geometry allows the use of thinner struts while still preventing contaminant accumulation. The angled leading edge creates flow currents that redirect contaminants inboard, eliminating the need for thicker struts and thereby reducing rotor drag compared to conventional radial strut designs

Inventive Principle:

Principle #4Asymmetry

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The forward-swept struts effectively reduce stringing and rotor drag, maintaining foil effectiveness and reducing power consumption by preventing contaminants and fibers from collecting on the strut and foil edges, thereby enhancing the efficiency of the pressure screen cylinder.

Implementation Method 1

The forward-swept struts create flow currents that move fibers and contaminants, which are dislodged from the pressure screen cylinder or from the general local flow field, inboard towards the hub of the rotor

Methodology Applied

Scientific EffectFlow currents: Convection

Data Source

PatentUS20260014591A1Rotor with forward-swept struts for pressure screen cylinders

Publication Date: 2026.01.15 KADANT BLACK CLAWSON LLC

AI summary

The present disclosure is directed to rotors for pressure screens with cylinders for screening solid contaminants from a solid slurry. The rotor comprising a cylindrical hub, at least one foil spaced radially outward from the cylindrical hub, and at least one strut coupling the at least one foil to the cylindrical hub, wherein the at least one strut is a forward-swept strut having a forward edge. Additionally disclosed are methods of using the rotor.